EP1516595A1 - Device for measuring the pressure between two pressed bodies - Google Patents

Abstract

Device for measuring the pressure between two bodies pressed against each other has at least an oscillator (1) with at least an induction coil (2), a sensor (11) made from at least partially conducting material that is arranged around the coil and an evaluation circuit (14) for determining the frequency change resulting from changes in the inductance of the induction coil caused by changes in the pressure applied to the sensor. The invention also relates to a corresponding use of the inventive device for determining the dental contact pressure or occlusion pressure between teeth.

Description

To determine the occlusion contact between two together For example, pressed bodies are used in the Dentistry off or discoloring films used in which the contact between upper and lower jaw teeth to a discoloration of the film, but also to a coloring the contact points on the teeth leads. Furthermore, can the film a color layer with a capsule enclosed Have dye. Depending on the on the Color coat pressure acting becomes a different Number of capsules broken and thus a different one Amount of dye released. An exact determination the strength of the compressive force, in particular the Occlusion pressure between teeth is through such films but not possible.

For Okklusionsdruckbestimmung therefore electrical Pressure sensors known. Thus, according to DE 31 17 284 A1, US Pat. No. 4,521,186 and EP 0 379 524 B1 use sensors, consisting of two layers each provided with tracks exist, between which a resistance layer is provided is. When pressure is applied to the bite section the sensor becomes the resistance between the tracks the two layers changed, and this change will recorded as a measured variable.

The known sensors are relative in construction and handling complicated, so they are compared to the conventional ones Occlusion contact films with discoloration not could prevail. In addition, the known sensors a relatively thick bite section, including the accuracy the occlusion measurement suffers. In addition, one must electrical contacting of the two layers with the Tracks for supplying the input and output signals respectively. Since the bite section for hygienic reasons with every patient must be changed, that is with associated with an additional effort.

Essentially the same disadvantages have occlusion pressure sensors based on the piezoelectric effect (eg US 4,592,727). In addition, the known piezo sensors have the disadvantage that they are prone to failure due to the required amplifier with a high impedance input resistance in adverse environmental conditions (such as water, dirt, oil, etc.).
DE 197 05 569 C1 turns away from the electrical sensors in the bite area and proposes instead an occlusion force transmission with a pressure fluid.

The object of the invention is to provide a simple structure Device for accurately determining the pressure between two bodies pressed together, in particular the dental contact pressure, to provide, for example, in Scope of dentistry similar to the previous one Occlusion film to be handled with discoloration can, and in particular no electrical contact in the Bite area required.

This is inventively marked with the in claim 1 Device achieved. In the subclaims 2 to 31 are advantageous embodiments of the invention Device re-given. In claims 32 to 37 are preferred uses of the invention Device and further advantageous embodiments indicated for these uses.

According to the invention is for determining the pressure between two bodies pressed together an oscillator with at least an induction coil provided. Instead of one Oscillators can also have two or more oscillators be provided, for example, a measuring and a reference oscillator. The difference of the frequency of the both oscillators audible e.g. after the so-called Beat buzzer principle.

To the induction coil is at least partially electrically arranged conductive sensor. With an evaluation circuit is the frequency change when changing the Inductance of the induction coil by an ohmic and / or capacitive and / or inductive influencing of the Sensor determined under pressure.

The pressure between the pressed bodies can According to the invention numerically determined by units of measurement or e.g. also as one not related to units relative measurement. By determining the pressure is also a distance determination between them compressed bodies possible.

In particular, with the device according to the invention allows for the addition of a top and a Mandible contact between dental teeth to determine. Through this dental contact pressure measurement will also determine the distance between allows the teeth pressed together.

However, not only the dental contact pressure determination is determined by the invention in a patient, but also at a dental model, which for the preparation of dentures may be required, such as a master cast, which is preferably in a dental articulator is possible.

In connection with the description of the dental contact pressure determination are not under the name "teeth" only the natural teeth, but also any kind of Dentures, especially restorative dentures like For example, fillings and inlays, but also everyone removable or fixed or combinable dentures such as dentures, dental crowns, dental bridges, Attachments or implants and their abutments too understand.

Under the dental contact pressure determination is particular the occlusion pressure determination between upper and lower jaw teeth to understand, but for example, the Lateral pressure determination between two adjacent teeth of the upper or lower jaw, for example, for determination of the interproximal distance.

The device according to the invention is in particular for determining the contact pressure between teeth Certainly, however, it can generally be used to determine the pressure between two pressed together bodies be used.

Hereinafter, however, the invention will be primarily in the Explained in connection with the dental contact pressure determination.

The oscillator of the device according to the invention has a certain natural frequency, for example, in the Range between 10 kHz and 1 GHz. The oscillator can be a self oscillating oscillator, or be excited by a vibration generator.

In principle, any known LC oscillator, such as Example Meissner, Hartley or Colpitts oscillator, RL and quartz generators also come in Consideration. Preferably, however, oscillators are used with inverters, in particular Schmitt trigger inverters, NAND and / or NOR gates are provided. These Oscillators are interesting because they have one have very simple and inexpensive construction. When a circuit has proven particularly suitable the one frequency-determining inductance as Transconductance between input and output at the inverter circuit used.

Under sensor in connection with the invention Device is not just the pressure-receiving area, but also every winding around the induction coil the oscillator can be arranged, as well as required connections, in particular electrical supply lines between pressure-receiving area and winding, to understand.

The sensor can, for example, by an electric conductive foil or an electrically conductive wire be formed. Furthermore, the sensor can, for example from a Piezoplättchen, in which the electrical Supply lines can be arranged around the induction coil formed become.

The electrically conductive leads, in particular the electrically conductive foil or the electrically conductive Wires are wound around the induction coil at least once of the oscillator wound. If several times around the induction coil be looped, the measuring effect strengthened.

The sensor can also be powered by a material with electric conductive properties are formed, which at least in the pressure-receiving area of the pressed together Body provided with an electrically insulating layer is. This electrically insulating layer can, for example by an electrically insulating plastic or for example also formed by a metal oxide become. This electrically insulating layer can under pressure of the pressed together body in Area of the contact surfaces are destroyed, thereby causing the contact resistance is affected. Thereby the device according to the invention can be applied to the most diverse Applications required measuring ranges by choosing the thickness of the electrically insulating Layer of the sensor can be tuned.

However, the sensor basically does not need any Pressure action destructible, electrically insulating Layer. Rather, it is possible to have a sensor use of electrically conductive material whose Transition resistance during compression between the two bodies or teeth changes, for example in the order of 0.1 mΩ to 100 mΩ, around a Frequency shift of the oscillator cause.

When the dental contact pressure is determined, the electric conductive foil, for example as a measuring strip be educated. Furthermore, the measuring strip can through a foil formed from an electrically conductive material and, for example, its inside, with a be provided electrically insulating layer. The electric conductive material is in particular a metallic one Material, for example an aluminum or copper material, So aluminum or an aluminum alloy or copper or a copper alloy. Instead of a metal foil However, for example, an electric conductive plastic film can be used. The electric For example, insulating layer of the measuring strip a metal oxide or, for example, a piezoelectric layer be. It is understood that in the presence of an electric insulating layer these only in that area the measuring strip must be provided between the is pressed against each other bodies or teeth. Also The measuring strip can be on the outside with an electric be provided insulating layer.

The sensor can also be made of an electrically conductive Material and an electrically insulating material with ferroelectric properties, for example from a electrically insulating layer with ferroelectric properties, be formed. Preferably for this purpose used piezoelectric materials. By the high Dielectric constant of these materials arises during Sensor an additional capacitive load leading to a Frequency change of the oscillator leads. The dielectric constant is by changing the pressure influenced between the bodies pressed together.

Another advantage of the device according to the invention is that when using a piezo element as part of the sensor no amplifier needed is because this as a capacitive load low impedance to the Sensor electronics is coupled. This becomes the provision the pressure between two pressed together Bodies even in adverse environmental conditions, in particular in the humid environment of dentistry.

The sensor, in particular the foil or the measuring strip, can also be made of a ferromagnetic material, in particular a ferromagnetic material with magnetoelasticity Properties are formed. So have become amorphous Alloys, so-called metallic glass, as suitable proved. Materials with magnetoelastic properties are characterized by the fact that their Permeability under mechanical load changes. By Use of materials with ferromagnetic properties is an improvement of the measuring effect by allows a greater influence on the inductance.

The preferably designed as a measuring strip sensor can consist of several layers that alternately an electrically conductive and an electrically insulating Material exist. In such a measuring strip form the layers of electrically conductive material several windings that are parallel to the expiration of the pressure the pressed together body activated one after the other can be. This will be determined by the number or the choice of Schichtmaterlien different Messund Proportional ranges enabled.

The sensor can be attached to the housing of the oscillator for example, with a self-adhesive layer be provided. It is also possible to use the measuring strip a spring clip to attach it to the housing. Also, it is possible the case of the oscillator be executed so that the sensor mechanically, for example with an open sleeve or spring clip similar to a pen, to be attached to it can.

There are many other ways to get the sensor and detachably connect the housing with each other. So can be provided on or in the housing openings through the sensor, which, for example, as a measuring strip is trained, plugged or threaded.

The sensor can also work on an electrically insulating material be upset. The material may e.g. paper or a plastic, in particular an elastic plastic, be. The plastic is preferably such that the sensor be cleaned by sterilization can.

The sensor is formed for example by a metal foil. As a metal, for example, precious metals, such as gold or Silver, in question, which is also based on an insulating substrate e.g. can be applied by vapor deposition.

A measuring strip made of an aluminum material which has been passivated on the inside with an aluminum oxide layer has proven particularly advantageous. The thickness of the aluminum oxide layer can be optimized by anodizing the aluminum strip. The measuring strip has a thickness of preferably less than 200 μm , in particular less than 100 μm . If the test strip is bitten, the electrically insulating layer can be destroyed at the occlusion sites. As a result, once the measuring strip has been wound around the induction coil, there is another winding around the induction coil that detunes the oscillator. This winding can load the inductance of the oscillator, for example in a transformer circuit. The frequency change caused by the detuning can cause both an increase and a decrease in the natural frequency of the oscillator, depending on the electromagnetic ratios in the frequency-determining oscillating circuit and the choice of the operating point.

Instead of or in addition to the induced inductive Strain can also change the frequency by a capacitive and / or ohmic load caused. Thus, by destruction of the insulating Layer formed winding to an ohmic resistance, Among other things of the mechanical contact depends on the occlusion sites.

Furthermore lie in the wound around the induction coil Measuring strips the two end sections of the measuring strip, on which the pressure to be determined acts, so on which is bitten, with its insides with the electric insulating or dielectric layer on each other. Thus, the measuring strip also forms a capacity which leads to a frequency change, depending on the as in the bite, the thickness of the dielectric layer and thus the distance of the electrically conductive Folienendabschnitte of the strip and the dielectric constant to change.

The evaluation circuit of the device according to the invention may be a phase lock loop (PLL) circuit and / or For example, a PC, the output signals of the oscillator or the PLL circuit are supplied.

The oscillator can be in a housing with a sleeve-shaped Section arranged around the the measuring strip is wound. Preferably, the oscillator is wireless connected to the evaluation circuit. For measuring the dental contact pressure it only needs the gauge strip the sleeve-shaped, for example, pencil-sized housing, to be looped once, after which the patient on the superimposed end portions of the housing around the Oscillator wound measuring strip bites. Of course can be the sensor or the foil or the measuring strip with the oscillator and / or evaluation circuit also be connected via a cable.

The measuring strip according to the invention preferably has a a conventional occlusion foil with discoloration corresponding Thickness and flexibility. He can be at his Outside additionally with a coating for detection the occlusion points by discoloration or discoloration be provided to gain further measurement data.

The output signals of the evaluation circuit, for example stored in a memory and / or a display be supplied. The ad can be, for example be formed by a bar of light emitting diodes.

As the device according to the invention in the low-resistance range works, it is through galvanic effects that e.g. can occur in saliva, not affected.

Figur 1

eine Ausführungsform der Schaltung der erfindungsgemäßen Vorrichtung;

Figur 2

verschiedene Kennlinien der Frequenzänderung bei auf den Messstreifen/Sensor einwirkender Kraft;

Figur 3

einen um das Gehäuse des Oszillators gewickelten Messstreifen in perspektivischer Wiedergabe;

Figur 4

schematisch den Okklusionsdruck vor und nach einer Dentalfüllung; und

Figur 5

eine um das Gehäuse des Oszillators gewickelte sekundäre Messwicklung mit einem Piezoelement in perspektivischer Wiedergabe.

The invention is explained in more detail by way of example with reference to the drawing. It shows:

FIG. 1

an embodiment of the circuit of the device according to the invention;

FIG. 2

different characteristics of the frequency change with force acting on the gauge / sensor;

FIG. 3

a measuring strip wound around the housing of the oscillator in perspective reproduction;

FIG. 4

schematically the occlusion pressure before and after a dental filling; and

FIG. 5

a wound around the housing of the oscillator secondary measuring winding with a piezoelectric element in perspective reproduction.

According to Figure 1, the oscillator 1 is a self-oscillating Oscillating circuit with an induction coil 2, several Capacities 3, 4, 5, two ohmic resistors 6, 7 and two Schmitt trigger inverters 8, 9 for forming the output signals on. The two Schmitt trigger inverters 8, 9 are with a not shown, for example, 5 V low voltage source (eg battery or battery).

The sensor 11 is designed as a measuring strip and how shown schematically in Figure 1, in transformer circuit arranged to the induction coil 2. Further is a secondary winding 12 with an ohmic resistor 13 or another load in transformer circuit to the Induction coil 2 is arranged. With the secondary winding 12th can the characteristic of the frequency change on exposure a force on the sensor 11 can be optimized.

The induction coil 2 can also be used as a differential transformer or Differential coil may be formed. This induction coil design is particularly advantageous when, As mentioned above, two or more oscillators are provided. A differential coil is then present when in Fig. 1, the winding 12 is omitted. On the other hand is the Winding 12 at the differential transformer present and symmetrical arranged to the primary winding 2.

FIG. 2 shows five different measuring characteristics A, B, C, D and E shown, wherein the characteristic A largely is unusable, while the characteristic B a long Proportional range, the characteristic C a shorter Proportional range and the characteristic D two proportional Has areas. The characteristic E shows an increase the oscillator frequency with increasing the measuring force.

The output signals of the inverter 9 become the evaluation circuit 14 fed, for example, by a PLL circuit can be formed, i. a circuit, which compares the input frequency with an internal frequency, and at a frequency difference, an output signal 15 generated. While from the Schmitt trigger inverter 9 generates a digital output signal for signal extraction becomes, by the PLL circuit an analog Output signal formed. This can with a not shown Analog-to-digital converter into a digital signal converted and in a memory device, not shown filed and on a likewise not displayed light-emitting diode bars are displayed. So For example, three to ten memory devices be present, allowing successively three to ten measurements be displayed on three to ten light bars can. This illustration allows the dentist who Bite force and the tooth spacing before, during and after the several times to measure the dental work to be performed.

According to FIG. 3, the oscillator 1 (FIG. 1) is in a sleeve-shaped, arranged about pencil-sized housing 16. The oscillator is, as indicated by the arrow 10, wirelessly connected to the evaluation circuit 14 (FIG. 1).

The measuring strip 11 is once in Figure 3 to the housing 16 in the region of the induction coil 2 (Fig. Its end portions 17, 18 thus form superimposed Flags. The measuring strip 11, which is an approximately a tooth corresponding width, for example from an aluminum foil, on its inside 19 provided with an insulating aluminum oxide layer is. To measure the occlusion pressure is on the bitten on one another flags 17, 18 bitten. This will at the occlusion site 20 destroys the alumina layer, or at least reduces its layer thickness, that a closed, electrically conductive winding arises, which determines the inductance and thus the frequency of the Oscillator 1 (Fig. 1) changes. To reinforce the measuring effect, can the measuring strip 11 also several times around the Housing to be wrapped. Also, the gauge strip may be off consist of a metal foil without insulating layer. Of the Contact resistance between the flags 17, 18 then hangs from occlusion pressure.

If, for example, according to FIG. 4, the patient has a filling in the mandibular tooth occluding with the upper jaw tooth 21 22, the occlusion pressure becomes (I) measured and stored as a reference before filling. Then, the tooth 22 according to (II) with the filling 23 provided and the filling ground (III), until the reference occlusion pressure is as before the filling (I). When inserting dentures such as Crowns, bridges, etc., it has to be advantageous proven when the pressure or the distance of the adjacent Teeth of the dentures before, during and after the insertion is determined in a reference measurement.

In FIG. 5, a secondary measuring winding 25 is several times round the housing 16 in the region of the induction coil 2 (FIG. 1) wound. The two leads 26 of the measuring winding 25 are connected to the two piezoelectric electrodes 27 of the piezoelectric element 24 connected. By applying pressure to the Okklussionsstelle 20, the piezoelectric element 24 as before described, thereby detuning the oscillator and thus allows the determination of the occlusion pressure.

Claims (37)

Device for determining the pressure between two bodies pressed against one another, characterized by at least one oscillator (1) having at least one induction coil (2), a sensor (11) made of an at least partially electrically conductive material which can be arranged around the induction coil (2), and an evaluation circuit (14) for determining the frequency change upon change of the inductance of the induction coil (2) by pressure on the sensor (11). Apparatus according to claim 1, characterized in that the oscillator (1) in addition to at least one induction coil (2) has at least one capacitor (3, 4, 5) and / or at least one resistor (6, 7). Device according to one of the preceding claims, characterized in that the sensor (11) has ferromagnetic properties. Apparatus according to claim 3, characterized in that the ferromagnetic sensor (11) has magnetoelastic properties. Device according to one of the preceding claims, characterized in that the oscillator (1) in a housing (16) is provided which has a portion with the induction coil (2), around which the sensor (11) can be arranged. Device according to one of the preceding claims, characterized in that the sensor (11) and / or the housing (16) are formed fastened to each other. Apparatus according to claim 6, characterized in that for attachment of the sensor (11) on the housing (16) of the sensor (11) and / or the housing (16) are provided with an adhesive layer and / or a spring clip. Device according to one of the preceding claims, characterized in that the pressure-receiving region of the sensor (11) and / or the winding around the induction coil (2) can be arranged attached to each other fastened. Device according to one of the preceding claims, characterized in that the sensor (11) is provided at least in the pressure-receiving region with an electrically insulating layer. Device according to one of the preceding claims, characterized in that the sensor (11) is at least partially formed by an electrically conductive foil and / or at least partially by an electrically conductive wire, which or at least once around the induction coil (2) can be wound , Device according to one of the preceding claims, characterized in that the sensor (11) is at least partially applied to an electrically insulating material. Apparatus according to claim 11, characterized in that the electrically insulating material is a plastic. Device according to one of the preceding claims, characterized in that the sensor (11) consists of at least one film of a plurality of layers, which alternately consist of an electrically conductive and an electrically insulating material. Device according to one of the preceding claims, characterized in that the electrically conductive foil and / or the electrically conductive wire have an electrically insulating layer. Apparatus according to claim 9 or 14, characterized gekennnzeichnet, that the electrically insulating layer having ferroelectric properties. Device according to one of the preceding claims, characterized in that the electrically insulating layer has piezoelectric properties. Device according to one of the preceding claims, characterized in that the electrically insulating layer is formed destructible by pressure. Device according to one of the preceding claims, characterized in that the electrically conductive foil is a metal foil. Apparatus according to claim 18, characterized in that the metal foil is an aluminum foil. Apparatus according to claim 19, characterized in that the aluminum foil on its inner side (19) has an aluminum oxide layer as an electrically insulating layer. Device according to one of the preceding claims, characterized in that the electrically conductive film is designed as a measuring strip. Device according to one of the preceding claims, characterized in that the sensor is formed from at least one piezoelectric element (24) which is connected to the secondary measuring winding (25) in the region of the induction coil (2). Apparatus according to claim 22, characterized in that the piezoelectric element in the pressure-receiving region has a thickness of at most 150 μ m, preferably at most 100 μ m. Apparatus according to claim 1, characterized in that the induction coil (2) is associated with a secondary winding (12) having a load (13) for optimizing the measuring characteristic (A, B, C, D, E). Device according to one of the preceding claims, characterized in that the induction coil is designed as a differential transformer and / or differential coil. Apparatus according to claim 1, characterized in that the evaluation circuit (14) is a phase-lock loop circuit. Apparatus according to claim 1, characterized in that the output signal of the oscillator (1) is supplied to a PC or a microcomputer. Apparatus according to claim 1, characterized in that the oscillator (1) is wirelessly connected to the evaluation circuit (14). Apparatus according to claim 1, characterized in that the output signal (15) of the evaluation circuit (14) is supplied to a display. Apparatus according to claim 29, characterized in that the display is formed by light-emitting diodes. Device according to one of the preceding claims, characterized in that a memory for storing the output signals (15) of the evaluation circuit (14) is provided. Use of the device according to one of the preceding Claims for the determination of dental contact pressure. Use according to claim 32, wherein as dental contact pressure the occlusion pressure between teeth is determined becomes. Use according to claim 32 or 33, wherein a sensor (11) with a tooth corresponding to the respective tooth Width is used. Use according to one of claims 32 to 34, wherein the sensor in the pressure-receiving region has a thickness of at most 100 μm , preferably at most 70 μm . Use according to any one of claims 32 to 35, wherein a sensor is used, which is in the area of the pressure surfaces of the teeth pressed together with a discoloring and / or discoloring coating for detection the occlusion contact points is provided. Use according to any one of claims 32 to 36, wherein a sensor is used in which the electric insulating layer in the area of the pressure surfaces of the Teeth pressed together from the discoloring and / or discoloring coating for detecting the Occlusion contact points is formed.

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